The Principles of Mens Rea and Actus Rea in Criminal Law Explained

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Mens rea and actus rea are important aspects of criminal law that are considered in court to determine the nature of a crime. The presence of these two conditions must be established before a criminal charge and the appropriate punishment can be determined.

In this article, we will take a close look at these two principles and find out how they impact a criminal case.

Mens Rea and Actus Rea in Criminal Law

Mens rea and actus rea are two important terms in criminal law in the western world. The terms are taken from the Latin sentence ‘Actus non facit reum nisi mens sit rea’ (an act does not make a person guilty unless the mind is also guilty).



Thus, mens rea refers to intention, while the actus rea refers to an action.

In any criminal case, the action, as well as the intention, must be established for a person to be charged with a crime. The degree and the kind of causation must also be considered. Also, all legitimate defenses, mitigating factors, and extenuating circumstances must be taken into account for a criminal charge to be determined.

The principles of mens rea and actus rea are part of the Modal Penal Code (MPC), which was developed by the American Law Institute in 1962. The modal law represents a seminal work that has greatly influenced criminal law in the US.

A person can be found guilty of a crime when he or she has committed the crime:

  • purposefully,
  • knowingly,
  • recklessly, or
  • negligently.

The first two of the above constitute more serious crimes and are categorized as “intentional” crime. The latter two are considered less serious crimes and are categorized as ‘unintentional’ crime. The two crimes entail different punishment.

For instance, suppose that Simon fired a shot at Jack with the intention to kill, but missed completely. However, several years later Simon “accidentally” ran over Jack who died as a result. In this case, Simon is not guilty of murder, but manslaughter, which entails less severe punishment.

In conclusion, mens rea and actus rea have important implications in criminal law. Both must be present for a person to be convicted of a crime. An experienced criminal defense lawyer will look at the evidence to see whether the crime was committed intentionally or unintentionally. The lawyer will gather the evidence and present it in the court in a manner that can result in a favorable outcome for the defendant.